Optical signal generators (e.g., lasers) are widely used in optical transmitters in wavelength division multiplexed (“WDM”) optical communication systems. Some optical signal generators use a distributed feed-back (DFB) laser for each channel of the WDM system. The optical signals generated by the multiple DFB lasers are then combined using elements such as arrayed waveguide grating based multiplexer or any other multiplexer. However, because a separate DFB laser is used for each channel, the optical transmitters tend to have increased complexity and cost. Further, the output wavelength of a DFB laser is relatively sensitive to temperature changes (i.e., thermal wavelength drift). For example, applications using DFB lasers need to provide special attention to wavelength stability over the desired temperature range, thereby increasing complexity and cost. Thus, reduction of this temperature dependency is important task on its own merits.
In addition, the optical transmitters typically require circuitry to monitor the power of the optical signal of each channel of the WDM system. This power monitoring circuitry is generally separate from the DFB laser devices (i.e., discrete), increasing the complexity and costs of fabricating the optical transmitters.
Still further, in many WDM applications, the power levels of the optical signals (of the various WDM channels) are equalized. Some approaches use separate attenuator circuits (e.g., thermo-optic Mach Zendher devices) to equalize the power between channels. Again, such circuitry tends to increase the complexity and cost of fabricating optical transmitters.